The present invention relates to a mattress having an innerspring unit with one or more compressible support members to increase the firmness of the mattress.
A mattress is typically formed of an innerspring unit, one or more layers of padding material disposed over the innerspring unit, and a mattress cover. The innerspring unit typically has two spaced-apart, rectangular border wires with a plurality of rows of helical spring coils disposed between the two border wires. The structure, size, wire gauge, and spacing of the coils typically determines the firmness of the mattress. The spring coils in adjacent rows may be oppositely wound or coiled to eliminate "roll together" and mattress "lean" conditions.
It is generally desirable to design a mattress so that it has increased firmness about its periphery so that when a person sits on the edge of a mattress it does not collapse. U.S. Pat. No. 3,822,426 to Mistarz discloses a mattress topper pad and border stabilizer. In one embodiment illustrated in FIG. 1 of the Mistarz patent, a relatively large amount of foam material is provided at the top and bottom portions of the mattress as well as along the side of the mattress between the edge of the mattress and the peripheral row of coils adjacent the edge of the mattress. That foam material substantially fills the entire interior space of the coils of the peripheral row. One disadvantage of this embodiment of the Mistarz patent is the requirement of a relatively large amount of foam material.
In a second embodiment shown in FIG. 6 of the Mistarz patent, the foam material is provided only at a portion of the side of the mattress adjacent the top and bottom convolutions of the coils in the peripheral row. Because the foam material is not provided in the coil convolutions between the top and bottom coil convolutions, the amount of stiffening provided by the foam material is limited.
U.S. Pat. No. 3,618,146 to Ferdinand discloses a border stabilizer for a mattress which is similar to the first embodiment of the Mistarz patent described above. In the Ferdinand patent, the foam material is provided between the periphery of the mattress and the interior areas of the peripheral row of coils.
U.S. Pat. No. 2,940,089 to Koenigsberg discloses a mattress structure in which a vertical layer of foam material is provided between the edge of the mattress and the peripheral row of coils. The vertical layer of foam material is generally uniform in width, except for a number of slots formed therein to receive a like number of edges of the innerspring unit of the mattress.
U.S. Pat. No. 2,826,769 to Drews discloses a border stabilizer for a mattress comprising a vertical layer of foam material provided between the edge of the mattress and the peripheral row of coils. In one embodiment shown in FIGS. 3 and 4, the side of the border stabilizer adjacent the edge of the mattress is flat, whereas the side of the border stabilizer is convexly curved to conform to the shape of the peripheral row of coils. In a second embodiment shown in FIG. 6, both sides of the border stabilizer are substantially flat, and the top and bottom convolutions of the spring coils extend into the foam border stabilizer while the middle convolutions of the coils abut the side of the border stabilizer.
U.S. Pat. No. 5,138,116 to Wagner, et al. discloses a method of stabilizing and reinforcing the border of a mattress in which a continuous length of foam material is wound about the periphery of the innerspring unit of the mattress between the edge of the mattress and the peripheral row of coils. The foam material substantially fills the interior portions of the coils in the peripheral row.
U.S. Pat. No. 5,239,715 to Wagner discloses a border stabilizing and reinforcing member for use in a mattress. The member is in the shape of a rhombus, having top and bottom portions of a relatively small width and a middle portion of a relatively large width.
U.S. Pat. No. 5,048,167 to Heffley, et al. discloses a method for restoring a used mattress in which rectangular blocks of resilient material are inserted between adjacent rows of coil springs in the mattress. The rectangular blocks are composed of three distinct layers of foam material, a central core layer and top and bottom layers. The material of the core layer may be composed of a stiffer material than the top and bottom layers.
U.S. Pat. No. 4,907,309 to Breckle discloses various embodiments of a mattress having rows of spring coils, each of which is provided in a pocket of fabric material. Connecting walls of foam material having various shapes are disposed between the rows of spring coil pockets.
In a prior art border or edge stabilizer for a coil spring mattress, illustrated in FIG. 1, an elongate, vertically contoured foam stabilizer strip 2 is provided between and spaced apart from outer peripheral rows 3, 4 of spring coils, which are shown schematically. The two vertically extending side walls 5, 6 of the stabilizer strip 2 are contoured so that the width of the stabilizer strip 2 narrows to a minimum at two different vertical points 7, 8. The widths of the top, middle and bottom portions of the stabilizer strip 2 are approximately equal. No part of the stabilizer strip 2 is disposed between any convolutions of the spring coils. When the spring coils are compressed, the convolutions of the coils do not substantially contact the sides of the stabilizer strip 2. Thus, the primary manner in which the mattress edge is stiffened is due to vertical compression of the stabilizer strip 2.